<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>响应式断点设置</title>
    <style type="text/css">
        /* 手机竖屏 */
        .demo{
            color: #000;
        }
        
        /* 手机横屏 */
        @media screen and (min-width: 480px) { 
            .demo{
                color: #999;
            }
        } 

        /* 平板竖屏 */
        @media screen and (min-width: 768px) { 
            .demo{
                color: red;
            }
        }

        /* 平板横屏及 PC 窄屏 */
        @media screen and (min-width: 1024px) { 
            .demo{
                color: blue;
            }
        }

        /* PC 宽屏 */
        @media screen and (min-width: 1200px) { 
            .demo{
                color: green;
            }
        }

        /* PC 超大屏 */
        @media screen and (min-width: 1380px) { 
            .demo{
                color: orange;
            }
        }
    </style>
</head>
<body>
    <div class="demo">默认颜色为黑色，视窗大小 >=480px为#999，>=768px为red，>=1024px为blue，>=1200px为green，>=1380px为orange</div>
</body>
</html>